The Universal Serial Bus (USB) is a connector standard that is in wide use. Currently, numerous standard bodies exist (USB 2.0) for enumerating requirements for implementation with USB connectors, including requirements for performance, hardware, form factor and various data transfer and connectivity protocols. As the USB connector becomes more popular and widespread, more applications and standards are adopted for the USB. In particular, there has been an effort to adopt standards by which the form factor of the USB becomes smaller, and has use in a variety of applications and environments in order to accommodate increasingly mobile and new computing devices.
As the name indicates, the USB connector acts as a data bus. In a standard mode of operation, the user is able to connect numerous devices to a single port using hubs. When devices are connected to a host, the host acts as a controller for all USB communications that enter through a particular port.
In general, the USB connector has a physical layer that includes hardware for implementing the data transfer protocol by which data is passed through the USB connector. The physical layer performs several functions, including serialization and de-serialization of transmissions, encoding and decoding of the signals. Across the USB connector, the protocol implemented provides for data packets that include token, data, and handshake packets.
Numerous standards have been and are currently being developed for the USB. These standards accommodate new smaller form factors, such as Mini-USB, as well as new data transfer protocols (e.g. USB 2.0). There is also a new standard for wireless USB ports. In addition, new standards accommodate use of USB connectors in various environments and applications. One standard is provided with “On-the-Go” which enables two devices connected through a USB port to negotiate for the role of the host. In particular, the On-The-Go Standard has introduced a Host Negotiation Protocol for enabling one device to act as host and controller in a one-to-one pairing.
Another more specific standard is the CEA-936A standard, which provides for use of Mini-USB connectors. Another new standard that has been implemented is the Micro-USB standard.
The trend towards smaller and more capable mobile computing devices has increasingly required more functionality and reduced dimensions from the connector interfaces of such devices The development of the Micro-USB standards has been part of the effort to enhance the usability of such connectors while reducing the dimensions of such connectors.
As an example, the USB CE 936A spec (also know as the USB-IF) specifies multiplexing data, analog audio and “mic” signals on two USB data pins (also called “D+” and “D−” pins). However, this configuration raises a problem: the connector cannot be used at the same time to transfer analog audio and digital data. Other shortcomings are present in this configuration as well. For example, under the standard, the mic and the right data channel are multiplexed onto to the same USB pin. This configuration precludes use of the connector as a stereo headset with a mic.
Numerous enhancements to standard USB connectors have been implemented. For example, one solution provides for the multiplexing of audio on to the data and ID pins to allow the use of analog headset via a physical adapter. This solution allows for the use of stereo headset with mic. However it also does not allow the use of digital devices at the same time as the analog headset that is in use.
In order to enhance the functionality of USB connectors, other solutions have provided for the use of extra pins. For example, some solutions have provided for physically augmenting a USB connector to allow for electrical and physical compatibility with other connectors of the same type, while adding extra pins for items such as analog audio and future expansion. However, such solutions have not worked under tight physical tolerances. Specifically, the configurations proposed for added pins have not accommodated limitations brought by the requirements of thin insulative housing structures and tight electrical termination tolerance required to achieve high data speeds (480 mbits per second at the current time with future expansion planned to 5 gbits per second).
FIG. 7A through FIG. 7E illustrate a prior art Micro-Universal Serial Bus (USB) connector, as adopted by the USB Implementers Forum, Inc. (“USB-IF”), in the UNIVERSAL SERIAL BUS MICRO-USB CABLES AND CONNECTORS SPECIFICATION, Revision 1.01 dated Apr. 4, 2007 (“Micro-USB Specification”). With reference to FIG. 7A, a front end view of a Micro-USB plug connector 700 as defined under the Micro-USB Specification is shown. The plug connector 700 includes a housing 710 having a mating structure 712 from which a set of electrical contacts 720 are provided. Part of mating structure 712 includes a shaped void 714 for receiving the corresponding mating structure of the receptacle connector (see FIG. 7B). The mating structure 712 may be formed from insulative material that is molded or otherwise shaped to retain the electrical contacts 720. Circuit elements (not shown) may carry signal lines from the electrical contacts to a connected device or cord.
The housing 710 and its mating structure 712 may include dimensions and an outward protruding shape that collectively defines the form factor of the plug connector 700. Both the form factor and the pin layout of the connector conform to the Micro-USB Specification, which dictates specific dimensions and pin assignments. In particular, the pin layout adopted by the USB-IF assigns each contact element to one of (i) a ground, (ii) voltage reference, (iii) identity, (iv) data (D+), or (v) D−.
FIG. 7B shows a receptacle connector 740 that is adapted to mate with the plug connector 700. The receptacle connector may also include a housing 750 with a mating structure 752, corresponding receptive void 754 (for receiving the mating structure of the plug connector) and set of electrical contacts 760 that conform to the Micro-USB Specification. As such, receptacle connector 740 can physically and electrically mate with the plug connector 700. Accordingly, the mating structure 752 may mirror that of the plug connector 700. Likewise, the set of electrical contacts 760 may include the pin layout of the plug connector, with the electrical contacts of each connector being aligned and positioned to electrically connect when the two connectors are mated.
With reference to FIG. 7A and FIG. 7B, the Micro-USB Specification provides for active physical connections to be formed between two mating connectors. Accordingly, the plug connector 700 includes biased securement tabs 730 that are extended outward and oriented to move inward towards a top surface 734 of the housing 710 for plug connector 700 when the receptacle connector 740 is engaged. Specifically, when the receptacle connector 740 is engaged, the tables 730 bias inward into the top surface 734 and enable the receptacle connector 740 to move over the plug connector 700 (where the corresponding mating structure 712, 752 of each connector 700, 740 aligns and mates with the corresponding void 714, 754 of each connector). The receptacle connector 740 may include corresponding recessed structures 762 which can align with the biased securement tabs to enable the securement tabs to extend and obstruct movement of the two connectors with respect to one another.
FIG. 7C illustrates conventional spring-type electrical contacts 770 that may be used on a Micro-USB connector. The spring-type electrical contacts 770 bias when engaged, and can cause an active electrical connection to be formed with an individual electrical contact. FIG. 7D illustrates a pad-type electrical contact 772 that may be used. The pad-type electrical contact 772 may mate with sprint electrical contacts 770 as shown in FIG. 7E.